Borrowings (Details Textual) (USD $)	Dec. 31, 2014	Dec. 31, 2013
Borrowings
Securities sold under agreements to repurchase	$ 397,107,000	$ 313,394,000
Investment securities pledged as collateral	1,673,263,000	1,635,316,000
FHLB advances	296,944,000	840,182,000
FHLB Put Options
Borrowings
FHLB advances	275,000,000
Minimum rate to exercise put option	8.00%
FHLB Advances, Due Date, Earliest	2015
FHLB Advances, Due Date, Last	2021
FHLB Advances, Interest Rate, Range from	2.73%
FHLB Advances, Interest Rate, Range to	3.64%
Repurchase Agreements
Borrowings
Investment securities pledged as collateral	523,855,000	398,447,000
Lines of Credit
Borrowings
Lines of credit	$ 255,000,000

Minimum rate to exercise put option.

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Amount of borrowings as of the balance sheet date from the Federal Home Loan Bank, which are primarily used to cover shortages in the required reserve balance and liquidity shortages.

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The earliest year of maturity for the advances from the Federal Home Loan Bank as of the Balance Sheet date.

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The last year of maturity for the advances from the Federal Home Loan Bank as of the Balance Sheet date.

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States the lowest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

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States the highest interest rate applicable to any of the advances from the Federal Home Loan Bank as of the Balance Sheet date.

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Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

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Amount, after the effects of master netting arrangements, of funds outstanding borrowed in the form of a security repurchase agreement between the entity and another party for the sale and repurchase of identical or substantially the same securities at a date certain for a specified price. Includes liabilities not subject to a master netting arrangement and not elected to be offset.

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Fair value of financial instrument held by the entity for its own account (proprietary securities) for trading or investment purposes that are carried at fair value and pledged to counterparties as collateral for financing transactions.

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